Devices are known for dispensing molten thermoplastic material that comprise a barrel member mounted on a frame and having an internal melting chamber communicating with an outlet opening through a nozzle, a sleeve having one end secured at the barrel member and a central opening communicating with the end of the melting chamber opposite the outlet opening which is adapted to receive a rod of solid thermoplastic material with one end portion of the rod in the melting chamber and the rod projecting through the sleeve along a predetermined path, and means for heating the barrel member to melt the end portion of the rod therein so that when the rod is pressed into the barrel member molten thermoplastic material will be expelled through the nozzle. U.S. Pat. Nos. 4,552,287 and 4,457,457 describe such devices. The device described in U.S. Pat. No. 4,457,457, also includes driving means in the form of an external compressed air power source adapted to be switched between activated and deactivated states for, when in the activated state, driving the rod of solid thermoplastic material into the melting chamber to expel molten thermoplastic material through the nozzle. While such devices are suitable for many purposes, they do not afford the precision needed to dispense molten thermoplastic material in many automated systems (e.g., robot operated systems) in that it is difficult to actuate the device in such a way that will produce a precise predetermined amount or rate of output from the device, and there is a tendency for some molten thermoplastic material to escape from the nozzle when the devices is not being activated to dispense material, which is undesirable or unacceptable for many automated applications.